Input interpretation
lead arsenite | molar mass
Result
Find the molar mass, M, for lead arsenite: M = sum _iN_im_i Plan: • Write the chemical formula and gather atomic masses from the periodic table. • Determine values for N_i and m_i using these items. • Finally, compute the mass. Write the chemical formula: As_2O_4Pb Use the chemical formula to count the number of atoms, N_i, for each element: | N_i As (arsenic) | 2 O (oxygen) | 4 Pb (lead) | 1 Look up the atomic mass, m_i, in g·mol^(-1) for each element in the periodic table: | N_i | m_i/g·mol^(-1) As (arsenic) | 2 | 74.921595 O (oxygen) | 4 | 15.999 Pb (lead) | 1 | 207.2 Multiply N_i by m_i to compute the mass for each element. Then sum those values to compute the molar mass, M: Answer: | | | N_i | m_i/g·mol^(-1) | mass/g·mol^(-1) As (arsenic) | 2 | 74.921595 | 2 × 74.921595 = 149.843190 O (oxygen) | 4 | 15.999 | 4 × 15.999 = 63.996 Pb (lead) | 1 | 207.2 | 1 × 207.2 = 207.2 M = 149.843190 g/mol + 63.996 g/mol + 207.2 g/mol = 421.0 g/mol
Unit conversion
0.421 kg/mol (kilograms per mole)
Comparisons
≈ 0.58 × molar mass of fullerene ( ≈ 721 g/mol )
≈ 2.2 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 7.2 × molar mass of sodium chloride ( ≈ 58 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 7×10^-22 grams | 7×10^-25 kg (kilograms) | 421 u (unified atomic mass units) | 421 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 421